Hardened "goop" (ferro-fluid) on midrange/tweeter speakers?

[Bill Webb]

I have come across several sets of speakers where one or more drivers
(midrange/tweeter) have siezed up. Opening them has revealed a black,
sticky tar-like (or harder) substance between the coil and magnet,
restricting motion of the coil. I assume this is (or was at one time)
ferro-fluid coolant. Is this correct? What causes it to harden this way?
Finally, is there any proper way to clear out this gunk or otherwise
restore the driver to normal?

Just recently I have picked up what would otherwise be a *beautiful* set
of speakers, except for a siezed-up midrange driver as described above.
While waiting for a response from the manufacturer about a replacement,
I figured I would see if it could be temporarily rejuvinated until the
replacement arrived - I put in a drop of nail polish remover to loosen
the gunk, removed as much as I could without making a project of it,
then fed in a couple drops of light machine oil (to roughly approximate
the original composition of the ferrofluid) and let the driver exercise
overnight on a signal generator. To my utter amazement, this hamhanded
ghetto-rigging actually worked! This driver sounds about the same (a
little louder, in fact) as the other. I don't know for how long, though,
but now it looks like I will be finding out: the maufacturer replies
that the part has been discontinued :(

[Jerry G.]

Most certainly the tweeter must be out of specs when doing all of this,
even though it may sound okay. If the unit is not available anymore, it
should be possible to match another one to fit in its place, with
similar specs. It would take some shopping around at parts dealers who
handle speakers.

Tweeters usually have this type of problem when they have been over
driven, and thus over heated at the voice coil.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Bill Webb" <sp...@cexx.org> wrote in message
news:JTZ3b.4662$Om1....@newsread2.news.atl.earthlink.net...

[Jim Adney]

On Sat, 30 Aug 2003 09:12:09 GMT Bill Webb <sp...@cexx.org> wrote:

>While waiting for a response from the manufacturer about a replacement,
>I figured I would see if it could be temporarily rejuvinated until the
>replacement arrived - I put in a drop of nail polish remover to loosen
>the gunk, removed as much as I could without making a project of it,
>then fed in a couple drops of light machine oil (to roughly approximate
>the original composition of the ferrofluid) and let the driver exercise
>overnight on a signal generator. To my utter amazement, this hamhanded
>ghetto-rigging actually worked! This driver sounds about the same (a
>little louder, in fact) as the other. I don't know for how long, though,

I believe ferro-fluid is just a mixture of oil and finely ground iron
(or some other magnetic material.) Your description sounds like the
oil has gotten overheated and either slowly evaporated or oxidized and
thickened. My first thought was to just try adding some heavy (low
vapor pressure, so it won't evaporate quickly) oil and see if it mixes
with what is in there and loosens up the speaker.

A better way to proceed might be to dig out a bit of the thick stuff
and try adding various oils to it to see what it seems to be happy
with.

-
-----------------------------------------------
Jim Adney jad...@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

[Bill Webb]

How do I find out the original specs for a proper match? The only
information I have is the size of the cone, spacing of the mounting
holes, and impedance. (Any kind of side-by-side listening test is ruled
out, since the driver's mate in the other speaker has almost certainly
been subjected to the same conditions that caused the other to gum up,
and may therefore be marginal too.) Will this information help in
finding a better acoustic match than trying to guess at what kind of oil
was in the original fluid?

All that said, I'm certainly no golden-ear audiophile, and probably
won't notice the difference from the manufacturer's original spec
(indeed, I've never heard how this pair originally sounded). (They're
not for a customer or anything, this pair will be for my own personal use.)

Thanks for the information about the possible cause of failure. Judging
from the thickness and blackness of the "goop" vs. the apparent age of
the set (they "appear" almost brand-new...OTOH, they can't be THAT new
if some of the drivers are discontinued), it appears they must have been
driven pretty hard.

[Dave Moore]

Try contacting these guys, tell em you're the CEO of a
international speaker repair company ;-)

http://www.fero.com/usa/audio_fluids_overview.htm

I'm just joking, honesty might work !!!

But if it doesn't :-)

"Bill Webb" <sp...@cexx.org> wrote in message

news:3F55AE19...@cexx.org...